Question

The general formula of disaccharide is ______________.
(A) \[{{\text{C}}_{12}}{{\text{H}}_{22}}{{\text{O}}_{10}}\]
(B) \[{{\text{C}}_{12}}{{\text{H}}_{22}}{{\text{O}}_{12}}\]
(C) \[{{\text{C}}_{12}}{{\text{H}}_{22}}{{\text{O}}_{11}}\]
(D) none of these

Answer 1

Hint: A disaccharide is made from two monosaccharide units by a condensation reaction. During the condensation reaction, a molecule of water is eliminated.

Complete answer:
Consider sucrose molecules. It is a disaccharide. It is made from glucose and fructose. Thus, the disaccharide sucrose has two monomers glucose and fructose. The general formula of glucose and sucrose are \[{{\text{C}}_6}{{\text{H}}_{12}}{{\text{O}}_6}\] and \[{{\text{C}}_6}{{\text{H}}_{12}}{{\text{O}}_6}\] respectively. Write the chemical reaction for the formation of one molecule of sucrose from one molecule of glucose and one molecule of fructose.
\[{{\text{C}}_6}{{\text{H}}_{12}}{{\text{O}}_6}{\text{ + }}{{\text{C}}_6}{{\text{H}}_{12}}{{\text{O}}_6}{\text{ }} \to {\text{ }}{{\text{C}}_{12}}{{\text{H}}_{22}}{{\text{O}}_{11}}{\text{ + }}{{\text{H}}_2}{\text{O}} \\
{\text{Glucose Fructose Sucrose Water}} \\\]
One glucose molecule contains 6 carbon atoms. One fructose molecule contains 6 carbon atoms. Total number of carbon atoms in one molecule of glucose and one molecule of fructose is 12. This is the same as the number of carbon atoms in one molecule of sucrose.
One glucose molecule contains 12 hydrogen atoms. One fructose molecule contains 12 hydrogen atoms. One water molecule contains 2 hydrogen atoms. Total number of hydrogen atoms in one molecule of glucose and one molecule of fructose is 24. This is the same as the total number of hydrogen atoms in one molecule of sucrose and one molecule of water. The number of hydrogen atoms in one molecule of sucrose is \[{\text{12 + 12}} - {\text{2 = 24}} - {\text{2 = 22}}\].
One glucose molecule contains 6 oxygen atoms. One fructose molecule contains 6 oxygen atoms. One water molecule contains 1 oxygen atom. Total number of oxygen atoms in one molecule of glucose and one molecule of fructose is 12. This is the same as the total number of oxygen atoms in one molecule of sucrose and one molecule of water. The number of oxygen atoms in one molecule of sucrose is \[6 + 6 - 1 = 12 - 1 = 11\] .
Hence, the general formula of sucrose is \[{{\text{C}}_{12}}{{\text{H}}_{22}}{{\text{O}}_{11}}\]
The general formula of disaccharide is \[{{\text{C}}_{12}}{{\text{H}}_{22}}{{\text{O}}_{11}}\]

Hence, the option (C) is the correct option.

Note: In a disaccharide, two monosaccharide units are joined by glycosidic bond. The glycosidic bond is an ether linkage.
Sucrose is the organic compound commonly known as table sugar.